Modeling of multi-overhead crane systems

Overhead cranes are commonly used in material handling systems where heavy loads must be moved with extraordinary precision. In many cases, several automatic cranes operate simultaneously in a system to perform various tasks. Since overhead cranes are high cost equipment, a good design is necessary for an efficient handling system. One major problem is finding an optimal assignment of cranes to incoming or outgoing loads. Since several cranes travel on the same runway, they frequently have to wait for each other before they accomplish their tasks. This crane interference makes the behavior of the system complex. Thus, the optimal assignment of cranes to loads becomes a problem whose analytical solution is almost impossible to find. Consequently, the XYCRANE model is developed to simulate the operations of multi-overhead cranes in an automated warehouse system. Engineers may use the model for designing new systems and for "fine-tuning" existing systems. The model is flexible so it can simulate various physical and operational characteristics of the system. Furthermore, the model can be adapted easily for other types of crane systems. Using XYCRANE, a simulation experiment is conducted for studying the behavior of an automated warehouse system with two overhead cranes. Then, the results of the experiment are used to construct hierarchically well-formulated models for predicting crane utilization, crane interference, and system throughput. These models show that factors interact to produce joint effects on the system performance.